According to conventional structures for electrical coupling between resonators and also between resonators and input/output terminals in dielectric filters of this type, as is described, for example, in Japanese Patent Laid-Open Nos. Sho 56-57302 and 55-35560, which correspond to U.S. Pat. Nos. 4,342,972 and 4,268,809 respectively, a dielectric is filled between inner and outer conductors to constitute a coaxial type dielectric resonator and a plurality of such resonators are arranged, or plural such resonators are arranged integrally using an outer conductor as a common conductor to constitute a dielectric filter, and there is used a dielectric block for capacitor coupling between resonators and between resonators and input/output terminals in such dielectric filter. The dielectric block for coupling is in the shape of a flat plate and is disposed in facing relation to the plural resonators of the dielectric filter. On the surface of the dielectric block there are formed electrode patterns which are each electrically coupled correspondingly to the inner conductor of each dielectric resonator. Further, the capacitance between adjacent resonators is adjusted to a preset value by selecting a suitable material of the dielectric block for coupling and by setting the capacitance of each coupling capacitor between the electrode patterns at a suitable value.
However, in the course of promotion of the reduction in size of such dielectric resonators the following problem arose. In the case of using a plurality of coaxial type dielectric resonators for constituting a dielectric filter, the distance between adjacent inner conductors becomes shorter with the reduction in size of the resonators, so it is unavoidable that the electrode patterns formed on the surface of the dielectric block for coupling also becomes smaller in size. Thus, with the reduction in size of the resonators, there arises the problem that the area of each electrode pattern becomes so small that a desired capacitance of each coupling capacitor is not obtained. In other words, in order to form electrode patterns planar on the surface of a flat plate-like dielectric block for coupling and obtain a desired capacitance of a coupling capacitor, it is necessary to ensure at least a minimum distance between the inner conductors of dielectric resonators, and this has been an obstacle to the reduction in size of a dielectric filter.